1. Field of the Invention
The present invention relates to novel hydrocarbon resin/polyphenylene ether comblike polymers, methods of preparing such polymers, and mixtures of these with polyphenylene ethers.
2. Discussion of the Background
Polyphenylene ethers, particularly poly(2,6-dimethylphenylene ether) (PPE), and methods for their preparation are known. See, for example, Buehler, "Special Plastics" (in German), pub. Akademieverlag, Berlin, 1978; and U.S. Pat. Nos. 3,306,874 and 3,306,875. And, for example, the preparation of PPEs by the oxidative coupling of ortho-substituted phenols mediated by copper-amine complexes in the presence of oxygen or oxygen-containing gas mixtures has proven itself to be an industrially feasible process.
Polyphenylene ethers are thermoplastics which are produced industrially in high volume. They are characterized by having high melting viscosities and high softening points. They are suitable for numerous technical applications requiring high heat deflection temperature. However, some properties of polyphenylene ethers are undesirable for certain technical applications. For example, molded parts made of polyphenylene ethers are excessively brittle because of their low impact strength. Processing these as melts has thus far not been industrially practicable to a great extent because the high temperatures required result in decomposition reactions which give the product an undesirable coloration.
It is known that the properties of polyphenylene ethers can be improved by admixture with other polymers. Thus, it is known from U.S. Pat. No. 3,383,435 and German AS 21 19 301 that the processibility of molten polyphenylene ethers can be improved by mixing-in polystyrene resins, preferably rubber-modified high impact polystyrenes (HIPS). In general, however, the properties of these materials in molding compounds of this type are not satisfactory. The molded pieces are frequently inadequate in impact strength and in heat deflection temperature.
Accordingly it has been proposed to increase the impact strength by addition of elastomeric block mixed polymers. Thus, e.g., German AS 19 32 234 and German OSs 24 34 848, 27 13 509 and 27 50 515 describe molding compounds comprised of styrene polymers, polyphenylene ethers and added compounds comprising differently structured hydrogenated or unhydrogenated block mixed polymers. The latter are primarily polymerized vinylaromatic hydrocarbon blocks and polymerized conjugated diene polymer blocks. In addition, U.S. Pat. Nos. 3,658,945, 3,943,191, 3,959,211, 3,974,235, 4,101,503, 4,101,504, 4,101,505 and 4,102,850 describe methods where the polystyrene component is modified by grafting with an ethylene-alpha-olefin-diene terpolymer. However, these methods have the drawbacks that it is costly to prepare the block mixed polymers and the graft product, and that the addition of these components is associated with a reduction in heat deflection temperature.
German OS 21 07 935 describes a method for preparing a mixture from a polyphenylene ether and a rubber. According to this method, a 2,6-disubstituted phenol is polymerized in the presence of a rubber such as, e.g., polyisoprene. In this way a product is obtained in which the identities of the mixing components--the polyphenylene ether and the rubber--are retained. This is demonstrated in very clear fashion by the fact that the components of the mixture can be re-isolated by suitable measures. For example, the mixture can be first dissolved in a suitable solvent and then a separation can be carried out by addition of a second solvent which does not dissolve one of the two components. This is also applicable for fine-particle powder mixtures comprised of polyphenylene ethers and rubber, which mixtures are obtained according to German Pat. No. 21 11 043.
Polyphenylene ethers and hydrocarbon resins are only slightly compatible with each other. Thus, addition of polyethylenes to polyphenylene ethers and to mixtures of polyphenylene ethers with polystyrene resins are limited to very small quantities of the added polyethylenes in order to prevent embrittlement and delamination (see European OS 0,080,666, p. 2, lines 4-10). The only improvement achieved thus far has been through the addition of compatibility-promoting agents, such as styrene-butadiene block copolymers.
According to a more recent method, 2,6-disubstituted phenols are oxidatively coupled in the presence of special manganese-amine catalysts, where the amino components are incorporated in the resulting polymer. The functionalized polyphenylene ethers obtained can be grafted with unsaturated compounds at elevated temperatures (see European OS 0,101,873). This method is accompanied by the risk of producing insoluble gel-like materials--as documented in the Examples, infra. In any event, the grafting method described is not likely to be industrially practicable because it is applicable only to specially prepared functionalized polyphenylene ethers.
Finally, it is known from German OS 17 45 201 that the chain length of polyphenylene ethers can be regulated by adding to the reaction mixture a phenol substituted by low molecular weight alkyl groups in positions 2, 4 and 6.
There is therefore a strongly felt need for a hydrocarbon resin component which is compatible with polyphenylene ethers. The compatible component should be facile to prepare, and should not reduce the heat deflection temperature of the product, cause embrittlement or delamination, or cause unwanted discoloration (e.g., producing insoluble materials). There is likewise a strongly felt need for a polyphenylene ether product containing such hydrocarbon resin.